Plasma film forming apparatus and plasma film forming method

ABSTRACT

A plasma film forming apparatus 1 includes: a vacuum chamber 2 in which a film forming process is performed to a substrate 4; a substrate holder 3 provided so as to be rotatable along a film forming surface 4a of the substrate 4; a rotating shaft 5 connected to the substrate holder 3; and a plasma generation unit 10 configured to generate a plasma 6 and provided such that an irradiation angle of the plasma 6 with respect to the rotating shaft 5 forms an acute angle. The apparatus further includes: a first driving unit 7 configured to move the substrate holder 3 in a vertical direction 11 parallel to the rotating shaft 5; a second driving unit 8 configured to move the substrate holder 3 in a horizontal direction 12 orthogonal to the rotating shaft 5; and a third driving unit 9 configured to rotate the rotating shaft 5, and the substrate holder 3 is moved independently in the vertical direction 11 and the horizontal direction 12.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application of International Patent Application No. PCT/JP2019/036408, filed on Sep. 17, 2019, which claims priority to Japanese Patent Application No. 2018-194965 filed on Oct. 16, 2018, each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a plasma film forming apparatus and a plasma film forming method for forming a film by irradiating a substrate such as a semiconductor substrate with plasma.

BACKGROUND

A technique is known in which the plasma generated by electron cyclotron resonance (ECR) is utilized and a voltage is applied to the ECR target arranged around the plasma, whereby ions contained in the plasma are accelerated and entered into the target to generate the sputtering phenomenon and target particles are adhered to a substrate to form a thin film.

As a manufacturing apparatus used for such a technique, for example, Japanese Unexamined Patent Application Publication No. 2005-281726 discloses a structure of a plasma film forming apparatus.

SUMMARY

Japanese Unexamined Patent Application publication No. 2005-281726 mentioned above discloses a structure of a plasma film forming apparatus including a sample chamber in which a rotatable sample substrate is stored and a plasma generation chamber (plasma generation unit) provided with a plasma generation source and connected to the sample chamber.

In the plasma film forming apparatus mentioned above, plasma is generated by utilizing electron cyclotron resonance by the interaction of microwave and magnetic field in the plasma generation chamber, and the generated plasma is irradiated from an oblique direction onto the sample substrate rotating in the sample chamber by using the divergent magnetic field, thereby forming a film on the sample substrate. The size of the plasma generation chamber is limited to about the wavelength of microwave (for example, 2.45 GHz), and it is difficult to increase the size. Therefore, in the plasma film forming apparatus mentioned above, the plasma generation chamber is arranged to be inclined so as to prevent the increase in size, and the plasma is irradiated to the sample substrate from an oblique direction.

Also, by irradiating the plasma to the sample substrate from an oblique direction, the irradiation range of the plasma to be irradiated to the sample substrate can be widened. Note that it is conceivable to incline the angle of the holder that holds the sample substrate with respect to the horizontal direction without arranging the plasma generation chamber to be inclined, but in this case, the holding mechanism of the sample substrate is complicated and the size of the apparatus is increased.

In recent years, there has been an increasing demand for a large-diameter sample substrate having a diameter of more than 200 mm. In the sputtering apparatus using ECR plasma, as the size of the sample substrate increases, factors such as the adjustment of the placement position of the sample substrate have a greater influence on the uniformity of the film thickness by the sputtering.

As a result of performing a simulation on a large-diameter sample substrate having a diameter of more than 200 mm in the ECR plasma film forming apparatus in which the plasma generation chamber was arranged to be inclined, the inventors found that sufficient film thickness uniformity could not be obtained only by the adjustment of the position of the sample substrate in the vertical direction in the case of the large-diameter sample substrate having a diameter of more than 200 mm.

Namely, the inventors found that, in the ECR plasma film forming apparatus in which the plasma generation chamber (plasma generation unit) is arranged to be inclined, the control range was narrow if the adjustment of the position of the sample substrate was limited to the adjustment in the vertical direction, and the control range of the film thickness was insufficient for the sample substrate having a large diameter.

An object of the present invention is to provide a technique capable of making the film thickness uniform even in the case of a substrate having a large diameter in the plasma film forming process.

The above-described object and novel features of the present invention will become apparent from the description of this specification and accompanying drawings.

An outline of a typical embodiment disclosed in this application will be briefly described as follows.

A plasma film forming apparatus according to an embodiment is a plasma film forming apparatus for performing a film forming process by irradiating a plasma, and the apparatus includes a vacuum container in which the film forming process is performed to a substrate and a substrate supporting unit configured to support the substrate in the vacuum container and provided so as to be rotatable along a film forming surface of the substrate. Further, the apparatus includes a rotating shaft connected to the substrate supporting unit and a plasma generation unit communicating with the vacuum container, configured to generate the plasma, and provided such that an irradiation angle of the plasma with respect to the rotating shaft forms an acute angle. Further, the apparatus includes a first driving unit configured to move the substrate supporting unit in a first direction parallel to the rotating shaft, a second driving unit configured to move the substrate supporting unit in a second direction orthogonal to the rotating shaft, and a third driving unit configured to rotate the rotating shaft, and the substrate supporting unit is moved independently in the first direction and the second direction.

Also, a plasma film forming method according to an embodiment is a plasma film forming method for performing a film forming process by irradiating a plasma, and the method includes the step of (a) supporting a substrate by a rotatable substrate supporting unit provided in a vacuum container. Further, the method includes the step of (b), in a state where the substrate supporting unit is being rotated, forming a film on the substrate by irradiating the plasma to the substrate such that an irradiation angle of the plasma with respect to a rotating shaft of the substrate supporting unit forms an acute angle and the step of (c) taking out the substrate from the vacuum container and measuring a distribution of film thickness of the film formed on the substrate. Further, the method includes the step of (d), based on a measurement result of the distribution of film thickness, moving the substrate supporting unit in a second direction orthogonal to a first direction parallel to the rotating shaft or the first direction and the second direction. Further, the method includes the step of (e), in a state where the substrate supporting unit is being rotated, forming a film on the substrate by irradiating the plasma to the substrate such that an irradiation angle of the plasma with respect to the rotating shaft of the substrate supporting unit forms an acute angle.

The effects obtained by the typical invention disclosed in this application will be described as follows.

The control range of a film thickness of a film formed on a substrate can be widened in the plasma film forming process, and the film thickness can be made uniform even in the case of the substrate having a large diameter without increasing the size of the plasma film forming apparatus. Also, it is possible to form a high-quality thin film.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a general configuration of a plasma film forming apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing a concept of movement of a substrate on the coordinate axes in the plasma film forming apparatus shown in FIG. 1;

FIG. 3(a) is a conceptual diagram of particle distribution at the time of sputtering in the plasma film forming apparatus shown in FIG. 1;

FIG. 3(b) is a conceptual diagram showing a shape of a film formed on a substrate;

FIG. 4(a) is a conceptual diagram of particle distribution at the time of sputtering in the plasma film forming apparatus shown in FIG. 1;

FIG. 4(b) is a conceptual diagram showing a shape of a film formed on a substrate;

FIG. 5(a) is a conceptual diagram of particle distribution at the time of sputtering in the plasma film forming apparatus shown in FIG. 1;

FIG. 5(b) is a conceptual diagram showing a shape of a film formed on a substrate;

FIG. 6 is a film thickness distribution diagram showing the distribution of film thickness on a substrate on which a film is formed using the plasma film forming apparatus shown in FIG. 1;

FIG. 7(a) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs=0 mm;

FIG. 7(b) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs=90 mm; and

FIG. 7(c) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs>90 mm.

DETAILED DESCRIPTION

An embodiment of the present invention will be described with reference to drawings.

Hereinafter, an embodiment of the present invention will be described with reference to drawings. FIG. 1 is a schematic diagram showing a general configuration of a plasma film forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a concept of movement of a substrate on the coordinate axes in the plasma film forming apparatus shown in FIG. 1.

In a plasma film forming apparatus 1 according to the present embodiment shown in FIG. 1, a plasma 6 is formed by generating ECR by the electric field of a microwave 16 and the magnetic field formed by a coil 15 provided around a plasma generation unit 10, and a film forming process by sputtering is performed by using the plasma 6 on a substrate 4 which is a sample such as a semiconductor wafer.

Also, in the plasma film forming apparatus 1 according to the present embodiment, the size of the substrate 4 on which the apparatus can form a film is, for example, 300 mm in diameter, and it is a film forming apparatus capable of performing the film forming process on the substrate 4 having a large diameter.

The plasma film forming apparatus 1 shown in FIG. 1 will be described. The plasma film forming apparatus 1 includes a vacuum chamber (vacuum container) 2 which is a process chamber in which the substrate 4 on which the film forming process is performed is placed and a plasma generation unit 10 which communicates with the vacuum chamber 2 and generates the plasma 6 in the vacuum chamber 2.

Further, a cylindrical target 13 is arranged at a position where the plasma generation unit 10 communicates with the vacuum chamber 2, that is, at the outlet of the plasma generation unit 10, and a sputtering material (film forming material) is provided on an inner wall of the target 13. At the time of film formation, RF (Radio Frequency) power 14 is applied to the target 13.

In addition, the coil 15 is provided around the plasma generation unit 10, and electrons in the plasma generated in the plasma generation unit 10 move into the vacuum chamber 2 along the magnetic field gradient. In doing so, ions are also drawn into the vacuum chamber 2 so as to be dragged by the potential formed by the electrons. At this time, by applying the RF power 14 to the target 13 to cause the ions in the plasma to collide with the target 13, a film can be formed on the substrate 4 by the sputtering action. When forming the film, process gas 17 is introduced from a gas introduction port 2 a of the vacuum chamber 2. The arrow P in FIG. 1 indicates the flow of sputtered particles as well as the flow of the plasma 6.

Since the size of the plasma generation unit 10 is limited to about the wavelength (12.2 cm) of the microwave 16 of 2.45 GHz, it is difficult to increase the size.

Therefore, in the plasma film forming apparatus 1 according to the present embodiment, in order to obtain high film thickness uniformity even for a large-diameter substrate 4 having a diameter of 300 mm without increasing the size of the plasma source (plasma generation unit 10), the plasma generation unit 10 is arranged to be inclined with respect to the substrate 4 and a mechanism capable of rotating the substrate 4 is provided.

Here, the details of the structure of the plasma film forming apparatus 1 shown in FIG. 1 will be described. The plasma film forming apparatus 1 includes a substrate holder (substrate supporting unit) 3 which supports the substrate 4 in the vacuum chamber 2 and is provided so as to be rotatable along a film forming surface 4 a of the substrate 4 and a rotating shaft 5 connected to the substrate holder 3. The substrate holder 3 has a holding portion 3 a that holds the substrate 4 and a connecting portion 3 b connected to the rotating shaft 5. The substrate 4 is merely placed on the holding portion 3 a of the substrate holder 3 and is not sucked or the like. At that time, the substrate 4 is placed on the holding portion 3 a with the film forming surface 4 a facing the target 13.

Note that the substrate 4 is placed on the substrate holder 3 and taken out from the substrate holder 3 along the horizontal direction of the substrate holder 3 through the space between the holding portion 3 a and the connecting portion 3 b.

Further, the plasma film forming apparatus 1 includes the plasma generation unit 10 which is configured to communicate with the vacuum chamber 2 and generate the plasma 6 and is provided such that an irradiation angle θ of the plasma 6 with respect to the rotating shaft 5 forms an acute angle. Namely, the plasma generation unit 10 is not arranged directly below the substrate 4, but is arranged to be inclined with respect to the film forming surface 4 a of the substrate 4. Consequently, the plasma 6 generated in the plasma generation unit 10 is irradiated from obliquely below to the film forming surface 4 a of the substrate 4. At this time, the irradiation range of the plasma 6 irradiated from obliquely below is widened, and the plasma 6 can be irradiated over the entire film forming surface 4 a of the substrate 4. Further, since the substrate holder 3 and the rotating shaft 5 are connected (coupled) such that a substrate mounting surface of the substrate holder 3 and the rotating shaft 5 form a substantially right angle, the irradiation angle θ of the plasma 6 irradiated from obliquely below to the film forming surface 4 a of the substrate 4 with respect to the rotating shaft 5 forms an acute angle (0<θ<90°).

As described above, in the plasma film forming apparatus 1, the plasma generation unit 10 is arranged to be inclined with respect to the film forming surface 4 a of the substrate 4. Namely, as shown in FIG. 2, the target 13 is also arranged to be inclined with respect to the film forming surface 4 a of the substrate 4. Since the size of the target 13 is also limited, the irradiation range of the plasma 6 is widened by arranging the target 13 to be inclined with respect to the film forming surface 4 a of the substrate 4, and the plasma 6 is irradiated over the entire surface even in the case of the large substrate 4. As a result, a film 21 (see FIG. 3) formed on the substrate 4 can be made uniform.

Further, the plasma film forming apparatus 1 includes a first driving unit 7 that moves the substrate holder 3 in the vertical direction (first direction, Z direction) 11 parallel to the rotating shaft 5, a second driving unit 8 that moves the substrate holder 3 in the horizontal direction (second direction, X direction) 12 orthogonal to the rotating shaft 5, and a third driving unit 9 that rotates the rotating shaft 5. The first driving unit 7 is a motor for moving up and down the substrate, the second driving unit 8 is a motor for horizontally moving the substrate, and the third driving unit 9 is a motor for rotating the substrate.

Therefore, in the plasma film forming apparatus 1, the substrate holder 3 is moved independently in the vertical direction 11 and the horizontal direction 12, respectively. Namely, in the plasma film forming apparatus 1, the substrate holder 3 on which the substrate 4 is placed can be moved independently in the vertical direction 11 and the horizontal direction 12, respectively.

Further, the plasma film forming apparatus 1 includes, on the vacuum chamber 2, a first operating shaft 7 a which is engaged with the first driving unit 7 and is provided in parallel to the vertical direction 11 and a second operating shaft 8 a which is engaged with the second driving unit 8 and is provided in parallel to the horizontal direction 12. The first operating shaft 7 a and the second operating shaft 8 a are, for example, ball screws. Further, an auxiliary operating shaft 7 b which is another ball screw is provided in parallel to the first operating shaft 7 a. The first operating shaft 7 a and the auxiliary operating shaft 7 b can move in synchronization with each other via a synchronization belt 7 d. In addition, an auxiliary operating shaft 8 b which is another ball screw is provided in parallel to the second operating shaft 8 a. The second operating shaft 8 a and the auxiliary operating shaft 8 b can move in synchronization with each other via a synchronization belt 8 d.

Further, a movable base plate 7 c provided along the horizontal direction 12 is engaged with the first operating shaft 7 a. The first driving unit 7 is provided on a fixed plate 7 f attached to the movable base plate 7 c. The movable base plate 7 c is also engaged with a guide pole 7 e installed in parallel to the first operating shaft 7 a, and is arranged so as to be able to move up and down. The movable base plate 7 c is also engaged with the auxiliary operating shaft 7 b and another guide pole 7 e provided in parallel to the auxiliary operating shaft 7 b on the side of the auxiliary operating shaft 7 b.

In addition, a supporting plate 8 e which is engaged with the second operating shaft 8 a and the auxiliary operating shaft 8 b is attached to an end of the movable base plate 7 c, and the second driving unit 8 is attached to a fixed plate 8 f attached to the supporting plate 8 e.

Also, the second operating shaft 8 a and the auxiliary operating shaft 8 b are provided with a movable plate 8 c which is engaged with both shafts. Further, a fixed plate 9 b is attached to the movable plate 8 c, and the third driving unit 9 is provided on the fixed plate 9 b.

In addition, on the movable base plate 7 c, an operating mechanism (horizontal movement mechanism) by the second driving unit 8 and an operating mechanism (substrate rotation mechanism) by the third driving unit 9 are provided. Specifically, a box-shaped first movable unit (movable unit) 20 a is provided on the movable base plate 7 c, and further, a conversion mechanism unit 18 that converts the rotation of a third operating shaft 9 a provided along the horizontal direction 12 into the rotation of the rotating shaft 5 provided along the vertical direction 11 is provided inside the box-shaped first movable unit 20 a. The conversion mechanism unit 18 is, for example, a bevel gear provided at each engaging portion of the third operating shaft 9 a and the rotating shaft 5, and is arranged inside a box-shaped second movable unit 20 b. Further, the second movable unit 20 b is arranged inside the box-shaped first movable unit 20 a. Namely, the first movable unit 20 a also covers the conversion mechanism unit 18 via the second movable unit 20 b, and is mounted on the movable base plate 7 c so as to be movable in the vertical direction 11.

Note that the second operating shaft 8 a is provided so as to penetrate from the outside to the inside of the box-shaped first movable unit 20 a, and an upper portion of the box-shaped second movable unit 20 b is engaged with the second operating shaft 8 a inside the first movable unit 20 a. Also, the second movable unit 20 b is connected to the movable plate 8 c via a connecting shaft 8 g.

In the structure described above, when the first operating shaft 7 a is rotated by the drive of the first driving unit 7, the auxiliary operating shaft 7 b is also rotated via the synchronization belt 7 d. Then, by the rotation of the first operating shaft 7 a and the auxiliary operating shaft 7 b, the movable base plate 7 c moves up or down (moves in the Z direction) together with the first driving unit 7 provided on the fixed plate 7 f while being guided by the guide poles 7 e.

Further, by the upward or downward movement (movement in the Z direction) of the movable base plate 7 c, the rotating shaft 5 which is a part of the mechanism (substrate rotation mechanism) operated by the drive of the third driving unit 9 moves up or down. Then, by the upward or downward movement of the rotating shaft 5, the substrate holder 3 moves up or down, and thus the substrate 4 also moves up or down. Namely, the position of the substrate 4 in the vertical direction 11 can be moved to a desired position by moving up or down the movable base plate 7 c.

Further, when the second operating shaft 8 a is rotated by the drive of the second driving unit 8, the auxiliary operating shaft 8 b is also rotated in synchronization via the synchronization belt 8 d. Then, when the second operating shaft 8 a and the auxiliary operating shaft 8 b are rotated, the movable plate 8 c engaged with both shafts moves in the horizontal direction 12. Namely, the movable plate 8 c moves in the horizontal direction 12 (moves in the X direction) by the rotation of the second operating shaft 8 a and the auxiliary operating shaft 8 b. Then, as the movable plate 8 c moves in the horizontal direction 12, the second movable unit 20 b connected to the movable plate 8 c via the connecting shaft 8 g moves in the horizontal direction 12 in the box-shaped first movable unit 20 a while being guided by the second operating shaft 8 a. Consequently, the rotating shaft 5 also moves in the horizontal direction 12. Further, by the movement of the rotating shaft 5 in the horizontal direction 12, the substrate holder 3 moves in the horizontal direction 12, so that the substrate 4 also moves in the horizontal direction 12. Namely, by the movement of the movable plate 8 c in the horizontal direction 12, the position of the substrate 4 in the horizontal direction 12 can be moved to a desired position.

Also, the third operating shaft 9 a provided along the horizontal direction 12 is rotated by the drive of the third driving unit 9, and further, the rotation of the third operating shaft 9 a is converted into the rotation of the rotating shaft 5 provided along the vertical direction 11 by the conversion mechanism unit 18 composed of bevel gears. Then, the substrate holder 3 is rotated by the rotation of the rotating shaft 5, so that the substrate 4 is also rotated along the horizontal direction 12. Namely, the substrate 4 can be rotated in the horizontal direction 12 by the rotation of the third operating shaft 9 a. Note that, in the plasma film forming apparatus 1, the rotation of the substrate 4 along the horizontal direction 12 is performed in the film forming process.

Also, the plasma film forming apparatus 1 includes a first bellows unit 19 a which is attached to the movable base plate 7 c so as to communicate the first movable unit 20 a and the vacuum chamber 2, surrounds a part of the rotating shaft 5, and keeps the inside of the vacuum chamber 2 in a vacuum atmosphere. Since the first bellows unit 19 a has a bellows structure and can be expanded and contracted, it follows the movement of the movable base plate 7 c in the vertical direction 11. Accordingly, even if the movable base plate 7 c moves in the vertical direction 11, the vacuum atmosphere of the first movable unit 20 a and the vacuum chamber 2 is maintained by the first bellows unit 19 a.

Further, in the plasma film forming apparatus 1, a second bellows unit 19 b which communicates with the vacuum chamber 2 via the first bellows unit 19 a and the first movable unit 20 a and surrounds a part of each of the third operating shaft 9 a and the connecting shaft 8 g is attached to the movable plate 8 c. Since the second bellows unit 19 b also has a bellows structure and can be expanded and contracted, it follows the movement of the movable plate 8 c in the horizontal direction 12. Accordingly, even if the movable plate 8 c moves in the horizontal direction 12, the vacuum atmosphere of the first movable unit 20 a and the vacuum chamber 2 is maintained by the second bellows unit 19 b.

In the plasma film forming apparatus 1 according to the present embodiment, the substrate 4 can be moved independently in the vertical direction 11 and the horizontal direction 12 in the vacuum chamber 2. Namely, the position of the substrate holder 3 can be moved independently in the vertical direction 11 and the horizontal direction 12, respectively. At the time of the film forming process by sputtering, only the rotation of the substrate 4 is performed, and the movement in the vertical direction 11 or the horizontal direction 12 is performed before the film forming process is started.

From the foregoing, it can be said that the plasma film forming apparatus 1 according to the present embodiment has a function capable of maintaining the uniformity of the film thickness of the film 21 formed on the substrate 4 even if the target 13 is worn or the conditions of film forming process are different.

Here, the concept of position adjustment of the substrate 4 in the plasma film forming apparatus 1 will be described with reference to FIG. 2. As shown in FIG. 2, the distance between the target 13 and the center of the film forming surface 4 a of the substrate 4 is defined as T−S, and the shift amount between the center of the target 13 and the center of the film forming surface 4 a of the substrate 4 is defined as Xs. The plasma film forming apparatus 1 includes a mechanism that can move the substrate 4 in the vertical direction 11 (Z direction) (vertical movement mechanism) and a mechanism that can move the substrate 4 in the horizontal direction 12 (X direction) (horizontal movement mechanism). For example, it is possible to change only T−S while fixing Xs, and conversely, change only Xs while fixing T−S.

Next, in the plasma film forming apparatus 1 according to the present embodiment, the distribution state of the particles sputtered from the target 13 will be described. FIGS. 3(a) and 3(b), FIGS. 4(a) and 4(b), and FIGS. 5(a) and 5(b) are conceptual diagrams of particle distribution at the time of sputtering in the plasma film forming apparatus shown in FIG. 1 and conceptual diagrams showing a shape of the film formed on the substrate. Note that the R part in each of FIGS. 3(a), 4(a), and 5(a) shows the distribution state of the sputtered particles, and the higher dot density in each R part indicates the larger distribution amount of the sputtered particles.

FIG. 3(a) shows the distribution amount of particles at the time of sputtering in the case where the center of the substrate 4 and the center of the target 13 substantially match with each other, and shows that the film forming rate is higher on the V1 side (high dot density) of the arrow V and the film forming rate is lower on the V2 side (low dot density) of the arrow V. Also, at the time of film formation, the substrate 4 is being rotated. In this case, as shown in FIG. 3(b), since the film forming rate is high near the center of the substrate 4, the amount of the film 21 to be formed is large and the distribution of film thickness has a convex shape.

FIG. 4(a) shows the distribution amount of particles at the time of sputtering in the case where the center of the substrate 4 is shifted to the right (horizontal direction away from the target 13) of the drawing. In this case, as shown in FIG. 4(b), since the film forming rate is higher near the outer peripheral portion of the substrate 4, the amount of the film 21 to be formed is larger near the outer peripheral portion. However, although the amount of film formed near the center is small, the film thickness is made uniform because the substrate 4 is being rotated.

FIG. 5(a) shows the distribution amount of particles at the time of sputtering in the case where the center of the substrate 4 is further shifted to the right (horizontal direction further away from the target 13) of the drawing. In this case, as shown in FIG. 5(b), since the film forming rate is still higher near the outer peripheral portion of the substrate 4, the amount of the film 21 to be formed is still larger near the outer peripheral portion. In addition, since the amount of film formed near the center is still smaller, the distribution of film thickness has a concave shape with a recess at its center because the substrate 4 is being rotated.

Therefore, in the plasma film forming apparatus 1 according to the present embodiment, it is preferable that the distribution of film thickness has the shape shown in FIG. 4(b). Thus, in the plasma film forming apparatus 1, as shown in FIG. 2, the center of the film forming surface 4 a of the substrate 4 and the center of the target 13 are shifted by the length of Xs (shift amount). Namely, the center of plasma irradiation is set at the position shifted from the center of the substrate 4, and the substrate 4 is rotated in the film forming process. As a result, the distribution of film thickness of the film 21 formed on the substrate 4 at the time of film formation has a convex shape near the outer peripheral portion, and the convex portion near the outer peripheral portion is added and the distribution is further averaged because of the rotation of the substrate 4. In this manner, the plasma film forming apparatus 1 can make the film thickness uniform.

As described above, in the plasma film forming apparatus 1, the sizes of Xs and T−S affect the uniformity of the film thickness. Also, the position of the substrate 4 in the vertical direction 11 or the horizontal direction 12 is adjusted before performing the film forming process such that the distribution of film thickness has the shape shown in FIG. 4(b). At that time, in the plasma film forming apparatus 1, each parameter in the vertical direction 11 and the horizontal direction 12 can be moved by, for example, each 1 mm. Consequently, the film forming position on the substrate 4 can be freely changed.

In the plasma film forming apparatus 1 according to the present embodiment, the mechanisms capable of independently moving the substrate 4 in the vertical direction 11 and the horizontal direction 12 are provided, and thus the control range of the film thickness of the film 21 formed on the substrate 4 can be widened. Further, the position of the substrate 4 can be flexibly moved, and the film thickness of the film 21 formed on the substrate 4 can be made uniform. For example, high film thickness uniformity can be obtained even for the large-diameter substrate 4 having a diameter of 300 mm. In addition, a high quality thin film can be formed.

Next, the plasma film forming method according to the present embodiment will be described. In the plasma film forming method according to the present embodiment, a film forming process by sputtering is performed using the plasma film forming apparatus 1 shown in FIG. 1.

First, the substrate 4 is conveyed into the vacuum chamber 2 of the plasma film forming apparatus 1 shown in FIG. 1, and the substrate 4 is placed on the rotatable substrate holder 3 provided in the vacuum chamber 2. At that time, the substrate 4 is inserted through the space between the holding portion 3 a and the connecting portion 3 b of the substrate holder 3, and the substrate 4 is placed on the holding portion 3 a such that the film forming surface 4 a of the substrate 4 faces downward (the film forming surface 4 a of the substrate 4 faces the target 13). In this manner, the substrate 4 is supported by the substrate holder 3. As the sputter material provided on the target 13, for example, any solid material such as aluminum, silicon, and tantalum can be used.

After the substrate is placed, in the state where the substrate holder 3 is being rotated along the horizontal direction 12 by the third driving unit 9 in the vacuum chamber 2, the film is formed on the substrate 4 by irradiating the plasma 6 onto the substrate 4 from the plasma generation unit 10 such that the irradiation angle θ of the plasma 6 with respect to the rotating shaft 5 of the substrate holder 3 forms an acute angle.

Specifically, the plasma 6 is formed by generating ECR by the electric field of the microwave 16 and the magnetic field formed by the coil 15 provided around the plasma generation unit 10. At the same time, the electrons in the plasma move into the vacuum chamber 2 along the magnetic field gradient generated by the coil 15.

In doing so, the ions are also drawn into the vacuum chamber 2 so as to be dragged by the potential formed by the electrons. At this time, by applying the RF power 14 to the target 13 to cause the ions in the plasma to collide with the target 13, the film is formed on the substrate 4 by the sputtering action. Also, when forming the film, process gas 17 is introduced from a gas introduction port 2 a of the vacuum chamber 2.

Further, the plasma film forming apparatus 1 includes the plasma generation unit 10 provided such that the irradiation angle θ of the plasma 6 with respect to the rotating shaft 5 of the substrate 4 forms an acute angle. Namely, the plasma generation unit 10 is arranged to be inclined with respect to the film forming surface 4 a of the substrate 4. Consequently, the plasma 6 generated in the plasma generation unit 10 is irradiated from obliquely below to the film forming surface 4 a of the substrate 4. At this time, the irradiation range of the plasma 6 irradiated from obliquely below is widened, and the plasma 6 is irradiated over the entire film forming surface 4 a of the substrate 4.

As a result, the desired film 21 is formed on the film forming surface 4 a of the substrate 4 by sputtering.

After forming the film, the substrate 4 is taken out from the vacuum chamber 2 and the distribution of film thickness of the film 21 formed on the substrate 4 is measured. When the substrate 4 is taken out from the substrate holder 3, the substrate 4 is taken out through the space between the holding portion 3 a and the connecting portion 3 b, and the substrate 4 is further conveyed to the outside of the vacuum chamber 2.

Then, after the substrate 4 is taken out from the vacuum chamber 2, the distribution of film thickness of the film 21 formed on the substrate 4 is measured. Next, after measuring the distribution of film thickness, the substrate holder 3 is moved in the horizontal direction 12 orthogonal to the vertical direction 11 parallel to the rotating shaft 5 or the vertical direction 11 and the horizontal direction 12 based on the measurement result of the distribution of film thickness. Namely, the position of the substrate 4 is adjusted such that the distribution of film thickness on the substrate 4 has the shape shown in FIG. 4(b).

In the present embodiment, as an example, the substrate holder 3 is moved in the horizontal direction 12. Namely, only the shift amount Xs between the center of the target 13 and the center of the film forming surface 4 a of the substrate 4 is adjusted without changing the distance T−S between the target 13 and the center of the film forming surface 4 a of the substrate 4.

Here, FIG. 6 is a film thickness distribution diagram showing the distribution of film thickness on a substrate on which a film is formed using the plasma film forming apparatus shown in FIG. 1, FIG. 7(a) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs=0 mm, FIG. 7(b) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs=90 mm, and FIG. 7(c) is a schematic diagram showing the distribution of film thickness on a substrate based on the measured value of FIG. 6 in the case of Xs>90 mm. Note that both FIG. 6 and FIG. 7 show the results of measurements or simulations in which the value of T−S is fixed at 295 mm (T−S=295 mm). Also, the film thickness uniformity in the distribution of film thickness of FIG. 7(a) is ±17.5%, and the film thickness uniformity in the distribution of film thickness of FIG. 7(b) is ±2.9%.

As a result of measuring the distribution of film thickness of the film 21 formed on the substrate 4 by the film forming process, when the distribution of film thickness is close to the shape of Xs=0 mm in FIG. 6, that is, the distribution of film thickness has a convex shape (in the case of FIG. 7(a)), the shift amount Xs between the center of the target 13 and the center of the substrate 4 is changed while fixing the distance T−S between the target 13 and the center of the film forming surface 4 a of the substrate 4 at 295 mm (without changing the distance T−S). Namely, by feeding back the measurement result of the distribution of film thickness of the film 21 formed on the substrate 4, only the shift amount Xs is changed to adjust the position of the substrate 4 while fixing the distance T−S at 295 mm. In this case, the substrate holder 3 is moved such that the shift amount Xs becomes larger than the shift amount Xs at the time of film formation for measurement. For example, the value of the shift amount Xs is adjusted to 90 mm (Xs=90 mm) in FIG. 6 (FIG. 7(b)). Actually, the moving distance X1 in the horizontal direction 12 to be input to the plasma film forming apparatus 1 is calculated from the shift amount Xs to be adjusted, and this X1 value is input.

In the plasma film forming apparatus 1 according to the present embodiment, the position of the substrate holder 3 can be moved independently in the vertical direction 11 and the horizontal direction 12, respectively. Therefore, it is possible to adjust the position of the substrate holder 3 (substrate 4) by moving it only in the horizontal direction 12.

After the substrate 4 is placed on the substrate holder 3 in the vacuum chamber 2 and the position of the substrate holder 3 is adjusted using the X1 value above, in the state where the substrate holder 3 is being rotated by the third driving unit 9, the film is formed again on the substrate 4 by irradiating the plasma 6 onto the substrate 4 from the plasma generation unit 10 such that the irradiation angle θ of the plasma 6 with respect to the rotating shaft 5 of the substrate holder 3 forms an acute angle.

As a result, as shown in FIG. 7(b), the film thickness of the film 21 formed on the substrate 4 can be made uniform.

Next, the case where the distribution of film thickness is close to the shape of Xs>90 mm in FIG. 6 as a result of measuring the distribution of film thickness of the film 21 formed on the substrate 4, that is, the center of the distribution of film thickness has a concave shape (the case of FIG. 7(c)) will be described.

When the center of the distribution of film thickness of the film 21 formed on the substrate 4 has a concave shape, the shift amount Xs between the center of the target 13 and the center of the substrate 4 is changed while fixing the distance T−S between the target 13 and the center of the film forming surface 4 a of the substrate 4 at 295 mm (without changing the distance T−S). In this case, the substrate holder 3 is moved such that the shift amount Xs becomes smaller than the shift amount Xs at the time of film formation for measurement. For example, the value of the shift amount Xs is adjusted to 90 mm in FIG. 6 (Xs=90 mm) (FIG. 7(b)). Actually, the moving distance X2 in the horizontal direction 12 to be input to the plasma film forming apparatus 1 is calculated from the shift amount Xs to be adjusted, and this X2 value is input.

Since the plasma film forming apparatus 1 according to the present embodiment can move the position of the substrate holder 3 independently in the vertical direction 11 and the horizontal direction 12, it is possible to adjust the position of the substrate holder 3 (substrate 4) by moving it only in the horizontal direction 12.

After the substrate 4 is placed on the substrate holder 3 in the vacuum chamber 2 and the position of the substrate holder 3 is adjusted using the X2 value mentioned above, in the state where the substrate holder 3 is being rotated by the third driving unit 9, the film is formed again on the substrate 4 by irradiating the plasma 6 onto the substrate 4 from the plasma generation unit 10 such that the irradiation angle θ of the plasma 6 with respect to the rotating shaft 5 of the substrate holder 3 forms an acute angle.

As a result, as shown in FIG. 7(b), the film thickness of the film 21 formed on the substrate 4 can be made uniform.

In the plasma film forming method above, the case where only the shift amount Xs is adjusted to move the substrate 4 in the horizontal direction 12 while fixing the distance T−S has been described, but the film may be formed again by adjusting only the distance T−S to move the substrate 4 in the vertical direction 11 while fixing the shift amount Xs. Alternatively, the film may be formed again by adjusting both the distance T−S and the shift amount Xs to move the substrate 4 independently in the vertical direction 11 and the horizontal direction 12.

In the plasma film forming method according to the present embodiment, after a film is formed once and the distribution of film thickness thereof is measured, the position of the substrate 4 is adjusted by moving the substrate holder 3 based on the measurement result in the horizontal direction 12 orthogonal to the rotating shaft 5 of the substrate holder 3 or both the vertical direction 11 and the horizontal direction 12, and the plasma 6 is irradiated to the substrate 4 to form the film again on the substrate 4 in this state.

Namely, by forming the film again after the position of the substrate 4 is adjusted to the position close to the position of the substrate 4 where the distribution of film thickness can be made uniform, obtained in advance by the simulation or the actual measurement, the control range of the film thickness of the film 21 formed on the substrate 4 can be widened, and the film thickness can be made uniform even in the case of the large-diameter substrate 4 without increasing the size of the plasma film forming apparatus 1. Also, it is possible to form a high-quality thin film.

Further, by irradiating the plasma 6 over the entire film forming surface 4 a of the substrate 4, the film 21 formed on the substrate 4 can be made to have a uniform thickness without being in a laminated state.

In the plasma film forming apparatus 1 according to the present embodiment, the plasma 6 can be obliquely irradiated to the substrate 4, and further the position of the substrate 4 can be adjusted not only in the vertical direction 11 but also in the horizontal direction 12. Originally, in a plasma film forming apparatus, moving the substrate 4 in the horizontal direction 12 is mechanically difficult as compared with moving the substrate 4 in the vertical direction 11, and a moving mechanism in the horizontal direction 12 is not provided if there is no need. However, the inventors have found the necessity of moving the substrate 4 in the horizontal direction 12 when performing the film forming process on the large-diameter substrate 4 having a diameter of 300 mm.

Namely, it is conceivable to irradiate the plasma 6 by simply shifting the substrate 4 in the vertical direction 11 and the horizontal direction 12, but when trying to adapt the plasma film forming apparatus to the large-diameter substrate 4, the amount of movement of the substrate 4 in the horizontal direction 12 needs to be increased, so that the size of the plasma film forming apparatus is increased. Further, there appears the region in which the plasma 6 is not irradiated, in the large-diameter substrate 4. If the state in which the plasma 6 is not irradiated and the state in which the plasma 6 is irradiated occur on the substrate 4, there is the possibility that the formed films 21 may be laminated (an interface may be formed in the film 21).

Therefore, as in the plasma film forming apparatus 1 according to the present embodiment, by irradiating the plasma 6 from obliquely below the substrate 4, the irradiation range of the plasma 6 can be widened as described above, and the plasma 6 can be irradiated over the entire film forming surface 4 a of the substrate 4. As a result, the film 21 formed on the substrate 4 can be made to have a uniform thickness without being in a laminated state.

If the plasma 6 is vertically irradiated from directly below the substrate 4 instead of oblique irradiation, it is not necessary to provide a moving mechanism of the substrate 4 in the horizontal direction 12, but the film formation range is narrowed in that case. Therefore, in the film forming process on the large-diameter substrate 4 having a diameter of 300 mm, it is important to irradiate the plasma 6 from obliquely below the substrate 4 as in the plasma film forming apparatus 1 according to the present embodiment. In addition, in the plasma film forming apparatus 1 according to the present embodiment, the substrate 4 can be moved independently in the vertical direction 11 and the horizontal direction 12, and thus the control range of the film thickness of the film 21 formed on the substrate 4 can be widened as described above, and the position control range of the substrate 4 can be adapted to the large-diameter substrate 4 without increasing the size of the plasma film forming apparatus 1. Further, the film thickness can be made uniform even in the case of the large-diameter substrate 4.

In the foregoing, the invention made by the inventors has been specifically described based on the embodiment, but the present invention is not limited to the embodiment described above and includes various modifications. For example, the embodiment above has been described in detail in order to make the present invention easily understood, and the present invention is not necessarily limited to the embodiment having all of the described configurations.

In the above-described embodiment, as a plasma film forming method, the case where, after a film forming process is first performed and the distribution of film thickness is measured, the position of the substrate 4 is adjusted by moving the substrate 4 in the horizontal direction 12 or both the vertical direction 11 and the horizontal direction 12 based on the measurement result, and then the film forming process is performed again has been described. As the above-described plasma film forming method, the data of the distribution of film thickness may be measured again at the time when the film forming process is performed on the substrate 4 multiple times after adjusting the position of the substrate 4 based on the measurement result of the distribution of film thickness, and the position of the substrate 4 may be adjusted again by moving it in the horizontal direction 12 or both the vertical direction 11 and the horizontal direction 12 based on this measurement result.

For example, when the film forming process is performed multiple times, the target material gradually decreases and the distribution of film thickness of the film 21 formed on the substrate 4 also changes at that time, and it is thus necessary to adjust the height of the substrate 4 again. At this time, if the height (position in the vertical direction 11) of the substrate 4 is changed to increase the distance T−S between the target 13 and the center of the film forming surface 4 a of the substrate 4, the film forming rate changes. However, in the plasma film forming apparatus 1 according to the above-described embodiment, since the substrate 4 can be moved in the horizontal direction 12, the film thickness can be made uniform and the above-mentioned rate does not change, and the film quality can be maintained at the same level. 

1. A plasma film forming apparatus for performing a film forming process by irradiating a plasma, the apparatus comprising: a vacuum container in which the film forming process is performed to a substrate; a substrate supporting unit configured to support the substrate in the vacuum container and provided so as to be rotatable along a film forming surface of the substrate; a rotating shaft connected to the substrate supporting unit; a plasma generation unit communicating with the vacuum container, configured to generate the plasma, and provided such that an irradiation angle of the plasma with respect to the rotating shaft forms an acute angle; a first driving unit configured to move the substrate supporting unit in a first direction parallel to the rotating shaft; a second driving unit configured to move the substrate supporting unit in a second direction orthogonal to the rotating shaft; and a third driving unit configured to rotate the rotating shaft, wherein the substrate supporting unit is moved independently in the first direction and the second direction.
 2. The plasma film forming apparatus according to claim 1, further comprising: a first operating shaft engaged with the first driving unit; and a second operating shaft engaged with the second driving unit, wherein the substrate supporting unit is moved in the first direction by operating the rotating shaft in the first direction by a rotation of the first operating shaft, and wherein the substrate supporting unit is moved in the second direction by operating the rotating shaft in the second direction by a rotation of the second operating shaft.
 3. The plasma film forming apparatus according to claim 2, further comprising: a third operating shaft engaged with the third driving unit; a conversion mechanism unit configured to convert a rotation of the third operating shaft into a rotation of the rotating shaft; and a first bellows unit configured to cover the conversion mechanism unit so as to communicate a movable unit moving along the first direction and the vacuum container, surround a part of the rotating shaft, and keep an inside of the vacuum container in a vacuum atmosphere.
 4. The plasma film forming apparatus according to claim 3, further comprising a second bellows unit configured to communicate with the vacuum container via the first bellows unit and the movable unit and surround a part of the third operating shaft.
 5. A plasma film forming method for performing a film forming process by irradiating a plasma, comprising the steps of: (a) supporting a substrate by a rotatable substrate supporting unit provided in a vacuum container; (b) after the step (a), in a state where the substrate supporting unit is being rotated, forming a film on the substrate by irradiating the plasma to the substrate such that an irradiation angle of the plasma with respect to a rotating shaft of the substrate supporting unit forms an acute angle; (c) after the step (b), taking out the substrate from the vacuum container and measuring a distribution of film thickness of the film formed on the substrate; (d) after the step (c), based on a measurement result of the distribution of film thickness, moving the substrate supporting unit in a second direction orthogonal to a first direction parallel to the rotating shaft or the first direction and the second direction; and (e) after the step (d), in a state where the substrate supporting unit is being rotated, forming a film on the substrate by irradiating the plasma to the substrate such that an irradiation angle of the plasma with respect to the rotating shaft of the substrate supporting unit forms an acute angle.
 6. The plasma film forming method according to claim 5, wherein, in the step (d), either of a distance between a target and a center of a film forming surface of the substrate or a shift amount between a center of the target and the center of the film forming surface of the substrate is adjusted by moving the substrate supporting unit in the second direction or the first direction and the second direction.
 7. The plasma film forming method according to claim 6, wherein, in the step (d), without changing the distance between the target and the center of the film forming surface of the substrate, the substrate supporting unit is moved such that the shift amount between the center of the target and the center of the substrate becomes larger or smaller than the shift amount at the time of the film formation in the step (b).
 8. The plasma film forming method according to claim 5, wherein, in the step (b) and the step (e), the plasma is irradiated over the entire film forming surface of the substrate. 